The invention pertains to the field of N-phenyl-N-(4-piperidinyl)amides having potent analgesic activity. A number of patents disclose certain N-phenyl-N-(4-piperidinyl)amides having analgesic activity such as, for example, U.S. Pat. Nos. 3,164,600; 3,998,834; 4,179,569; 4,584,303; and 4,167,574. The analgesic compounds of this invention differ structurally from the prior art compounds, for example, by di-substitution in the 3-position of the piperidine ring with both an OR.sup.1 and a methyl substituent, wherein said OR.sup.1 is hydroxy or straight chained lower alkoxy.
European patent application EP 309,043 (Van Daele et al) discloses mono-substitution by a hydroxy or lower alkoxy in the 3-position of the piperidine ring. Not only is di-substitution in this position not disclosed, but significant structural variances at other positions are indicated and, furthermore, the compounds are non-analgesics. Mono-substitution in the 3-position is also shown with a methoxy substituent by N. Lalinde et al., Abstr. Pap. Am. Chem. Soc. (197 Meet., MEDI 31, 1989), and with a methyl substituent in European patent application EP 383,579.
The invention also provides certain novel synthetic intermediates for making formula ( I ) compounds.